Update index.js to allow for language additions from outside of the API

[rawr51919]

Updates index.js to allow for language additions from outside of the API (carryover from unmaintained upstream PR matheuss#31).

[vitalets]

Good feature! Could you add to readme a usage example?

[rawr51919]

Good feature! Could you add to readme a usage example?

Sure. I can reference what the original upstream PR had for instructions and mirror those in the readme if you like.
The new feature allows for things like this to be done (code again from matheuss#31):

Gta = require('google-translate-api');
Gta.languages['sr-Latn'] = 'Serbian Latin';
Gta.languages['sr-Cyrl'] = 'Serbian Cyrillic';

EDIT: Done.

[codecov-io]

Codecov Report

Merging #18 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #18   +/-   ##
=======================================
  Coverage   92.42%   92.42%           
=======================================
  Files           2        2           
  Lines          66       66           
=======================================
  Hits           61       61           
  Misses          5        5

Impacted Files	Coverage Δ
index.js	90.19% <100%> (ø)	⬆️

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[vitalets]

This is cool! 👍
Please

• rebase to master to resolve conflicts in readme
• add test for that feature

[rawr51919]

The repo's been rebased around the current master. The test for this will be worked on shortly.

[rawr51919]

I've coded a WIP test for this particular feature. Testing would be very much appreciated.

[vitalets]

Thank you! 👍